Add MS Edge to Autoprefixer config

Add http://wkbug.com/150715 to Wall of Browser Bugs

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Trivially simplify IE10 Mobile viewport bug workaround

Update to Jekyll v3.0.0.

See the IE9 note in https://developer.mozilla.org/en-US/docs/Web/CSS/%3Ahover#Browser_compatibility
The prereqs to trigger the bug are still present in v4.
/fyi @mdo

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Per http://caniuse.com/#feat=documenthead , document.head is supported in IE Mobile 10+,
so slightly simplify the JS accordingly.

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Remove http://wkbug.com/149935 from Wall of Browser Bugs

It's been fixed in WebKit Nightly!
See https://trac.webkit.org/changeset/191623 and http://wkbug.com/149366
Refs #17438, #14237

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Adding autocomplete attribute in docs input search

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Make heading class styles trump heading element styles

Remove empty line from _grid.scss

Change "$use-hover..." to proper "$enable-hover..."

Fix #18076

Trivially simplify heading margin-bottom declarations

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Add !important to text alignment utility classes

Use the `border-radius` mixin for `.label-pill`

Minor grammar tidy-up on Utilities doc page
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See http://trac.webkit.org/changeset/191610
Refs #17913
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Update typography docs re: global vars
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Use Jekyll configuration for blog/slack URLs
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Switch to jQuery 2.x.x.

This reuses the existing URLs in the docs Jekyll configuration rather than hard coding.

Refs #17913
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v4 docs Missed navbar color scheme name changes

Change d6b6a20a missed two doc mentions
of the previous names when changing to new:
    .navbar-default  -->  .navbar-light
    .navbar-inverse  -->  .navbar-dark

Refs #15947
Somehow c256aca1 got lost during the SCSS translation...

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